The present invention is generally directed to circuit monitoring devices, and more particularly, to an improved fault indicator.
Various types of fault indicators have been constructed for detecting electrical faults in power distribution systems, including clamp-on type fault indicators, which clamp over a cable of the system and derive their operating power from the magnetic field surrounding the cable, and test-point mounted type fault indicators, which attach to test point sockets provided on connectors or other system components and derive their operating power by means of a capacitive coupling to the monitored conductor. In addition, either type of fault indicator may be either self-resetting, wherein the fault indication is automatically reset following resumption of current flow in the condictor, or manually reset, wherein an operator must manually clear a fault indication.
In previous fault indicators of either type detection and indication of fault currents has typically been accomplished by circuitry including a reed switch positioned in close proxmity to the monitored conductor, and an electromagnetic indicator actuated by the circuitry to either fault or reset indicating positions. Upon occurrence of a fault current, the reed switch closes momentarily and a current is caused to flow through a magnetic winding to magnetize a magnetic pole assembly, which magnetically positions a movable indicator, typically a rotatably mounted flag member visible from the exterior of the indicator housing, to a fault-indicating position. In self-resetting indicators, a reset current remagnetizes the magnetic pole assembly to reposition the flag member to a reset-indicating position.
The use of electromagnetic indicators in such prior fault indicators, while providing satisfactory performance, undesirably complicated their manufacture by requiring the fabrication, assembly and adjustment of a number of precision parts of different materials. Moreover, the physical size of practical electromagnetic indicators prevented a desired reduction in the size of prior fault indicators, and such electromagnetic indicators could not readily provide an indication to the user as to whether the monitored conductor was powered.
The present invention overcomes these drawbacks by providing a fault indicator which incorporates a high impedance non-mechanical electronic indicator in the form of a liquid crystal display. This results in an improved fault indicator which is more compact and easier to manufacture, and which provides in a preferred construction an indication to the user as to whether the monitored line is powered.
Accordingly, it is a general object of the present invention to provide a new and improved fault indicator.
It is a more specific object of the present invention to provide a fault indicator which avoids the use of electromechanical indicator mechanisms.
It is a still more specific object of the invention to provide a fault indicator which is more compact and easier to manufacture.
It is a still more specific object of the invention to provide a fault indicator which provides both, fault and line powered circuit status indications.